test: 后端测试从 SQLite 全面切换到 MySQL，与生产环境对齐

测试库不再使用 SQLite 内存库，改为每个测试包独立的 MySQL 库，
表结构由 backend/migrations 的真实迁移建立。

基础设施
- 新增 internal/database/testdb.go：NewTestDB() 保持原签名（28 处调用零改动），
  内部连接 MySQL 测试库，首次调用重建库并执行全部真实迁移，之后每次调用清空全表
- 库名 = 测试库基础名 + 包目录名，同包共享、跨包隔离，使 go test ./... 可并发执行
  （共用一库时各包会互相 DROP/CREATE 导致 database exists）
- 新增 NewDryRunDB()：MySQL 方言 + DryRun，供断言 SQL 形态的 5 处测试使用
- 新增 AutoMigrateIfMissing()：只对不存在的表 AutoMigrate，
  避免改动迁移定义的索引与约束
- 新增 scripts/prepare-test-db.sh：建库与通配授权，可重复执行
- 33 处 sqlite.Open 全部替换，26 个测试文件改用 MySQL
- 删除 46 处手写 SQLite 方言 DDL（AUTOINCREMENT / INTEGER PRIMARY KEY / TEXT），
  表统一由真实迁移建立
- go.mod 移除 gorm.io/driver/sqlite 与 mattn/go-sqlite3
- 删除生产代码里 distribution/repository.go 的 sqlite 方言分支（strftime）

对齐环境后暴露并修复的真实问题
- DATE(col) 在 MySQL 返回 DATE 类型，使 Date string 字段变成 RFC3339 时间串，
  大盘日期会带出时间部分；28 处改为 DATE_FORMAT(col, '%Y-%m-%d')
- 系统自动创建分销结算批次时 created_by 写入 0，违反指向 admin_users 的外键，
  生产会直接插入失败；改为写 NULL（新增 adminRef helper）
- MySQL DATETIME 仅到秒，静默截断 Go 侧写入的时间，
  导致租用时长计算与结算时点回读比对偏差；
  rental_orders 的 9 个业务时间列提到 DATETIME(6)
- 测试数据补齐严格模式要求的 NOT NULL 列、修正超出列长的取值、补齐外键父记录

迁移
- 000065 的 ALTER TABLE rental_orders 一并完成业务时间列精度调整，
  feature 侧不再单开迁移文件

脚本与文档
- check.sh / check-backend-coverage.sh 去掉 -p 1 串行与 SQLite 相关注释
- 更新 docs/Repository层测试补充总结.md 的测试运行说明

backend/internal/modules/order/repository_integration_test.go

@@ -279,7 +279,7 @@ func TestRepositoryCreateAppliesRenterGrowthDiscount(t *testing.T) {
 
 func TestCreateOrderSnapshotsShelfMarkup(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.DistributionSite{}, &model.DistributionSiteAccount{}, &model.DistributionRuleVersion{}, &model.DistributionOrderFinancial{}, &model.DistributionOrderParty{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.DistributionSite{}, &model.DistributionSiteAccount{}, &model.DistributionRuleVersion{}, &model.DistributionOrderFinancial{}, &model.DistributionOrderParty{}); err != nil {
 		t.Fatal(err)
 	}
 	repo := NewRepository(db)
@@ -859,7 +859,7 @@ func TestCancelPendingHandoffKeepsAssetsUntilRefundApproved(t *testing.T) {
 		t.Fatalf("create account failed: %v", err)
 	}
 	listing := model.RentalListing{
-		ListingNo:     "LST-REFUND-REVIEW-001",
+		ListingNo:     "LST-REFUND-REV-001",
 		OwnerID:       owner.ID,
 		AccountID:     account.ID,
 		Status:        listingStatusRented,
@@ -1319,7 +1319,7 @@ func TestAdminResetRenterConfirmTimeoutRefreshesStageTime(t *testing.T) {
 
 func TestAdminForceHandoffStartsNormalOwnerOrder(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.Dispute{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.Dispute{}); err != nil {
 		t.Fatalf("migrate disputes failed: %v", err)
 	}
 	repo := NewRepository(db)
@@ -1387,7 +1387,7 @@ func TestAdminForceHandoffStartsNormalOwnerOrder(t *testing.T) {
 
 func TestAdminForceHandoffAbnormalOwnerTimeout(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.Dispute{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.Dispute{}); err != nil {
 		t.Fatalf("migrate disputes failed: %v", err)
 	}
 	repo := NewRepository(db)
@@ -1460,26 +1460,26 @@ func TestOwnerConfirmCheckoutAfterTimeout(t *testing.T) {
 	}
 
 	listing := model.RentalListing{
-		OwnerID:       owner.ID,
-		AccountID:     account.ID,
-		Status:        listingStatusRented,
-		ReviewStatus:  listingReviewStatusApproved,
-		PriceCent:     1000,
+		OwnerID:      owner.ID,
+		AccountID:    account.ID,
+		Status:       listingStatusRented,
+		ReviewStatus: listingReviewStatusApproved,
+		PriceCent:    1000,
 	}
 	if err := db.Create(&listing).Error; err != nil {
 		t.Fatalf("create listing failed: %v", err)
 	}
 
 	order := model.RentalOrder{
-		OrderNo:          "ORD-CHECKOUT-TIMEOUT-001",
-		ListingID:        listing.ID,
-		AccountID:        account.ID,
-		OwnerID:          owner.ID,
-		RenterID:         renter.ID,
-		Status:           orderStatusAbnormal,
-		HandoffStatus:    handoffStatusOwnerCheckoutConfirmTimeout,
-		SettlementStatus: settlementStatusPending,
-		RentAmountCent:   1000,
+		OrderNo:           "ORD-CHECKOUT-TIMEOUT-001",
+		ListingID:         listing.ID,
+		AccountID:         account.ID,
+		OwnerID:           owner.ID,
+		RenterID:          renter.ID,
+		Status:            orderStatusAbnormal,
+		HandoffStatus:     handoffStatusOwnerCheckoutConfirmTimeout,
+		SettlementStatus:  settlementStatusPending,
+		RentAmountCent:    1000,
 		DepositAmountCent: 0,
 	}
 	if err := db.Create(&order).Error; err != nil {
@@ -1526,7 +1526,7 @@ func TestOwnerConfirmCheckoutAfterTimeout(t *testing.T) {
 
 func TestAdminForceHandoffUsesExistingOwnerRecordAndRejectsPlatformOrderBeforeHandoff(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.Dispute{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.Dispute{}); err != nil {
 		t.Fatalf("migrate disputes failed: %v", err)
 	}
 	repo := NewRepository(db)
@@ -1607,7 +1607,7 @@ func TestAdminForceHandoffUsesExistingOwnerRecordAndRejectsPlatformOrderBeforeHa
 
 func TestAdminForceHandoffStartsPlatformManagedOrderAfterPlatformHandoff(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.Dispute{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.Dispute{}); err != nil {
 		t.Fatalf("migrate disputes failed: %v", err)
 	}
 	repo := NewRepository(db)
@@ -2017,7 +2017,7 @@ func TestPlatformManagedCheckoutIncludesConsumableAndDepositCompensation(t *test
 
 func TestAdminPlatformCheckoutDisputeCreatesArbitrationCase(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.Dispute{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.Dispute{}); err != nil {
 		t.Fatalf("migrate dispute failed: %v", err)
 	}
 	repo := NewRepository(db)
@@ -2217,7 +2217,7 @@ func TestAdminPlatformCheckoutConfirmRequiresExplicitConfirmationForZeroOwnerInc
 
 func TestListForUserAndFindForUserSiteIsolation(t *testing.T) {
 	db := setupOrderTestDB(t)
-	if err := db.AutoMigrate(&model.DistributionSite{}); err != nil {
+	if err := database.AutoMigrateIfMissing(db, &model.DistributionSite{}); err != nil {
 		t.Fatalf("migrate distribution_sites err: %v", err)
 	}
 	repo := NewRepository(db)

backend/internal/modules/order/repository_test.go

@@ -5,13 +5,12 @@ import (
 	"testing"
 	"time"
 
+	"hfb_sys/backend/internal/database"
 	"hfb_sys/backend/internal/model"
 	"hfb_sys/backend/internal/modules/rentergrowth"
 	"hfb_sys/backend/internal/timeutil"
 
 	"gorm.io/datatypes"
-	"gorm.io/driver/sqlite"
-	"gorm.io/gorm"
 )
 
 func pureCoinDiscountOrder() model.RentalOrder {
@@ -504,10 +503,7 @@ func TestNewOrderNoUsesShanghaiTimeWhenLocalIsUTC(t *testing.T) {
 }
 
 func TestApplyAdminOrderFiltersSmartRouting(t *testing.T) {
-	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{DryRun: true})
-	if err != nil {
-		t.Fatalf("打开测试数据库失败: %v", err)
-	}
+	db := database.NewDryRunDB()
 
 	tests := []struct {
 		name        string